1. Field
This disclosure relates generally to semiconductors, and more specifically, to transistors made using a fin.
2. Related Art
The use of semiconductor fins has been found to be very useful in making transistors that, for a given area, have more drive and less leakage. The making of fins, however, present a number of challenges. In practice there are many different processes that are involved in making a transistor that is both manufacturable and realizes the potential of a finFET. For example, there are a number of processes that typically are used in making the required features. For example, there is generally preparation used prior to actually forming a gate dielectric. These preparation steps can have adverse affects on the structures. For example, a clean that is used in preparation for gate dielectric formation has been found to undercut the fin. The clean typically is for removing the same type of material as the underlying insulating layer. Similarly, sidewall spacer formation is more involved than simply applying a conformal layer followed by an anisotropic etch. A protective layer, which is under the sidewall spacer, is typically removed which, when performed, can also etch into an underlying oxide. These are problems that can be more troubling than is immediately apparent. For example, if these etches result in undercutting, the undercut regions can be the location for stringers. These stringers, if bad enough, can actually short elements, such as gates, together. Further, they can degrade performance or leave undesirable materials for the remaining processes.
Accordingly, there is a need for a technique for finFETs that removes or improves upon one or more of the problems described above.